X-rays are generated by the bombardment of energetic electrons on a metal surface. In this setting, an x-ray source is a device comprising an electron emitter known as the cathode and an electron receiver known as the target or anode. The anode is the x-ray emitter. The cathode and the anode are arranged in a particular configuration, and are enclosed in a vacuum housing. Moreover, an x-ray system may comprise the following components: the x-ray source, the computerized manipulation and handling device, the detectors, and the power unit(s). Moreover, in combination with other technology areas, x-ray finds applications in medical imaging, security inspection, and nondestructive testing in industry. Computer technology has revolutionized the use of x-ray in modern society, for example, x-ray CT scanner (computed tomography). The advancement in detector technology allowed improved energy resolution, digital images and continuously increasing scan areas. However, the technology for generating x-ray has essentially been the same since the birth of the Coolidge tube for about 100 years ago, when William Coolidge revolutionized the way x-ray were generated by replacing the gas-filled tubes with an evacuated tube, housing a hot tungsten filament to utilize thermionic emission.